Russian arms trafficker Viktor Bout, the 'Merchant of Death' has been sentenced to 25 years in prison. Photograph: AP

Viktor Bout, the notorious Russian arms dealer dubbed 'the Merchant of Death', has been sentenced to 25 years in prison following his conviction on terrorism charges resulting from a US sting operation.

Bout, 45, had faced a mandatory minimum of 25 years in prison and a maximum life sentence when he faced US district judge Shira Scheindlin in Manhattan. He was arrested in Thailand four years ago, and held there until his extradition to the US for trial in late 2010.

The judge also ordered a $15m forfeiture.

The sentencing came after the government portrayed Bout as one of the world's worst villains, capable of empowering dictators in war-torn countries by supplying weapons that they could turn on their own people.

The defence had countered that Bout was a political prisoner, a victim of a sting operation that made it seem as if he hated Americans and was willing to sell surface-to-air missiles to a Colombian terrorist organisation to shoot down American helicopters.

The government had asked for Bout to be imprisoned for life. A defence lawyer requested that the jury verdict be reversed and the charges dismissed.

Bout told the judge he was "not guilty" and said allegations against him were false.

When a prosecutor said in court on Thursday that Bout agreed to sell weapons to kill Americans, Bout shouted, "It's a lie!" He told the judge he "never intended to kill anyone" and said, "God knows this truth."

Prosecutors said that Bout's weapons fuelled armed conflicts in some of the world's most treacherous hot spots, including Rwanda, Angola and the Congo and that he was looking for new arms deals in places such as Libya and Tanzania when he was arrested.

Bout, the inspiration for an arms dealer character played by Nicolas Cage in the 2005 film "Lord of War," has maintained that he was a legitimate businessman who wasn't selling arms when the American operatives knocked on his door.

Federal prosecutors said the government initiated its investigation in 2007 because Bout "constituted a threat to the United States and to the international community based on his reported history of arming some of the world's most violent and destabilising dictators and regimes."

"Although Bout has often described himself as nothing more than a businessman, he was a businessman of the most dangerous order," prosecutors said in their pre-sentencing memo.

"Transnational criminals like Bout who are ready, willing and able to arm terrorists transform their customers from intolerant ideologues into lethal criminals who pose the gravest risk to civilized societies."

Defense attorney Albert Dayan wrote in a letter to the judge that the United States targeted his client vindictively because it was embarrassed that his companies helped deliver goods to American military contractors involved in the Iraq War.

The deliveries occurred despite United Nations sanctions imposed against Bout since 2001 because of his reputation as a notorious illegal arms dealer, Dayan said.

The lawyer noted that the US Department of the Treasury imposed its own ban on dealings with Bout in July 2004, citing in part the "unproven allegation" that Bout made $50m in profits from arms transfers to the Taliban when Osama bin Laden and al-Qaida were based in Afghanistan.

The Merchant of Death moniker was attached to Bout by a high-ranking minister at Britain's Foreign Office, who had drawn attention to his 1990s notoriety for running a fleet of aging Soviet-era cargo planes to conflict-ridden hotspots in Africa.

The nickname was included in the US government's indictment of Bout, and US Attorney Preet Bharara referenced it when he announced Bout's extradition in late 2010, saying: "The so-called Merchant of Death is now a federal inmate."